/*
 * Copyright 2002-2018 the original author or authors.
 *
 * Licensed under the Apache License, Version 2.0 (the "License");
 * you may not use this file except in compliance with the License.
 * You may obtain a copy of the License at
 *
 *      http://www.apache.org/licenses/LICENSE-2.0
 *
 * Unless required by applicable law or agreed to in writing, software
 * distributed under the License is distributed on an "AS IS" BASIS,
 * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
 * See the License for the specific language governing permissions and
 * limitations under the License.
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package org.springframework.aop.target;

import java.io.Serializable;

import org.springframework.aop.TargetSource;
import org.springframework.lang.Nullable;
import org.springframework.util.ObjectUtils;

Canonical TargetSource when there is no target (or just the target class known), and behavior is supplied by interfaces and advisors only.
Author:Rod Johnson, Juergen Hoeller
/** * Canonical {@code TargetSource} when there is no target * (or just the target class known), and behavior is supplied * by interfaces and advisors only. * * @author Rod Johnson * @author Juergen Hoeller */
public final class EmptyTargetSource implements TargetSource, Serializable {
use serialVersionUID from Spring 1.2 for interoperability.
/** use serialVersionUID from Spring 1.2 for interoperability. */
private static final long serialVersionUID = 3680494563553489691L; //--------------------------------------------------------------------- // Static factory methods //---------------------------------------------------------------------
The canonical (Singleton) instance of this EmptyTargetSource.
/** * The canonical (Singleton) instance of this {@link EmptyTargetSource}. */
public static final EmptyTargetSource INSTANCE = new EmptyTargetSource(null, true);
Return an EmptyTargetSource for the given target Class.
Params:
  • targetClass – the target Class (may be null)
See Also:
/** * Return an EmptyTargetSource for the given target Class. * @param targetClass the target Class (may be {@code null}) * @see #getTargetClass() */
public static EmptyTargetSource forClass(@Nullable Class<?> targetClass) { return forClass(targetClass, true); }
Return an EmptyTargetSource for the given target Class.
Params:
  • targetClass – the target Class (may be null)
  • isStatic – whether the TargetSource should be marked as static
See Also:
/** * Return an EmptyTargetSource for the given target Class. * @param targetClass the target Class (may be {@code null}) * @param isStatic whether the TargetSource should be marked as static * @see #getTargetClass() */
public static EmptyTargetSource forClass(@Nullable Class<?> targetClass, boolean isStatic) { return (targetClass == null && isStatic ? INSTANCE : new EmptyTargetSource(targetClass, isStatic)); } //--------------------------------------------------------------------- // Instance implementation //--------------------------------------------------------------------- private final Class<?> targetClass; private final boolean isStatic;
Create a new instance of the EmptyTargetSource class.

This constructor is private to enforce the Singleton pattern / factory method pattern.

Params:
  • targetClass – the target class to expose (may be null)
  • isStatic – whether the TargetSource is marked as static
/** * Create a new instance of the {@link EmptyTargetSource} class. * <p>This constructor is {@code private} to enforce the * Singleton pattern / factory method pattern. * @param targetClass the target class to expose (may be {@code null}) * @param isStatic whether the TargetSource is marked as static */
private EmptyTargetSource(@Nullable Class<?> targetClass, boolean isStatic) { this.targetClass = targetClass; this.isStatic = isStatic; }
Always returns the specified target Class, or null if none.
/** * Always returns the specified target Class, or {@code null} if none. */
@Override @Nullable public Class<?> getTargetClass() { return this.targetClass; }
Always returns true.
/** * Always returns {@code true}. */
@Override public boolean isStatic() { return this.isStatic; }
Always returns null.
/** * Always returns {@code null}. */
@Override @Nullable public Object getTarget() { return null; }
Nothing to release.
/** * Nothing to release. */
@Override public void releaseTarget(Object target) { }
Returns the canonical instance on deserialization in case of no target class, thus protecting the Singleton pattern.
/** * Returns the canonical instance on deserialization in case * of no target class, thus protecting the Singleton pattern. */
private Object readResolve() { return (this.targetClass == null && this.isStatic ? INSTANCE : this); } @Override public boolean equals(Object other) { if (this == other) { return true; } if (!(other instanceof EmptyTargetSource)) { return false; } EmptyTargetSource otherTs = (EmptyTargetSource) other; return (ObjectUtils.nullSafeEquals(this.targetClass, otherTs.targetClass) && this.isStatic == otherTs.isStatic); } @Override public int hashCode() { return EmptyTargetSource.class.hashCode() * 13 + ObjectUtils.nullSafeHashCode(this.targetClass); } @Override public String toString() { return "EmptyTargetSource: " + (this.targetClass != null ? "target class [" + this.targetClass.getName() + "]" : "no target class") + ", " + (this.isStatic ? "static" : "dynamic"); } }